Electronic sphygmomanometers that measure blood pressure using arterial pressure information detected from the upper arm, wrist or finger are in widespread use, and accurate measurement of blood pressure is desired.
Causes of fluctuation in blood pressure measurements can be roughly divided into fluctuation attributable to the person who is being measured (blood pressure fluctuation or error due to the measurement method) or fluctuation attributable to the device (abnormality of pressure sensor). The latter cause, in particular, is avoidable by periodically calibrating the device.
However, sphygmomanometers purchased for household use are generally not calibrated, except under specific circumstances such as when they malfunction. Thus, even if, for example, the output of the pressure sensor, which is vital in measuring blood pressure, is outside a stipulated tolerance range, there is no way of knowing this, and it is uncertain whether the measured blood pressure value is correct or not. Thus, in the case where there is a large difference between the measured blood pressure value and the normal blood pressure value, it is uncertain whether the blood pressure itself has fluctuated or whether the measured blood pressure value has fluctuated due to a pressure sensor error, giving the person being measured cause for concern.
Also, some sphygmomanometers for use in medical facilities are equipped with two pressure sensors, and monitor pressure based on the output of these pressure sensors. However, the functions of the two pressure sensors are used for different purposes. In other words, blood pressure is calculated with cuff pressure information obtained with one of the pressure sensors, and abnormality detection is performed based on the output of the other pressure sensor. Specifically, when the detected pressure value of the other pressure sensor greatly exceeds 300 mm Hg, for example, an abnormality is detected. In this case, safety is ensured by stopping the pump and opening the valve. This ensuring of safety is a requirement of the medical standard IEC 60601-2-30.
One example of a sphygmomanometer that is equipped with a plurality of pressure sensors and monitors operation failure of the pressure sensors is shown in the Patent Literature 1.